154 RELATIONS OF SOIL TO HEAT 



atmosphere surrounding a globe. It is at once evident that 

 the vertical rays falling on the globe pass through a thinner 

 stratum of air than the rays falling on the same point from 

 a smaller angle, the maximum amount of atmospheric inter- 

 ference occurring plainly at sunrise and sunset. 



The facts we have just brought forward not only elucidate 

 the influence of latitude on climate, they also help to explain 

 the well-known effect of aspect on the fertility of land. In 



BAG 



FIGURE 6. 

 i 



our northern hemisphere a field or garden facing or sloping 

 towards the south will for most purposes be greatly preferred 

 to one sloping towards the north, and will yield much earlier 

 crops. The inclination towards the south does indeed^ in 

 part counteract the prejudicial effect of north latitude, and 

 causes the sun's rays to fall at a higher angle upon the 

 surface. 



In Figure 6 we have a flat surface BC, divided into two 

 equal portions AB and AC, and receiving equal solar radia- 



